littorina
Lit"to*ri"na, n. Etym: [NL. See Littoral.] (Zoöl.) Defn: A genus of small pectinibranch mollusks, having thick spiral shells, abundant between tides on nearly all rocky seacoasts. They feed on seaweeds. The common periwinkle is a well-known example. See Periwinkle.